This invention relates to a method and an apparatus for drying washed objects, and more particularly to a method and an apparatus for rinsing and drying objects such as semiconductor wafers, glass substrates or the like which have been washed.
Drying of a precision substrate such as a finely-formed or fined wafer, glass substrate or the like following washing thereof is importantly affected by a degree at which a moisture entering trenches thereof is removed therefrom. In view of such a situation, a drying apparatus in which vapor of an organic solvent is used has been conventionally put to practice for this purpose. The drying apparatus using organic solvent vapor is constructed in such a manner as shown in FIG. 10 by way of example. More specifically, the drying apparatus includes a drying tank 40 and a heater 41 mounted on an outer surface of a bottom of the drying tank 40. The drying tank 40 is charged therein with an organic solvent 42, which is heated to a boiling point thereof by means of the heater 41, so that vapor of the organic solvent 42 may be formed in an upper region or portion of the tank 40. Then, objects 43 such as wafers or the like which have been subjected to washing and rinsing using water or the like are placed in the vapor. This results in the organic solvent which is evaporated more readily than water being condensed on a surface of the object 43 while being substituted for water adhered to the surface of the object 43.
The objects 43 in the vapor are gradually increased in temperature to a vapor temperature or boiling point of the organic solvent 42 and then taken out of the vapor atmosphere, resulting in the solvent adhered to the objects 43 being rapidly evaporated due to reduced latent heat thereof, leading to completion of drying of the objects 43. The drying tank 40 has a cooling coil 44 arranged in the upper portion thereof, which functions to condense the organic solvent evaporated by heating. The organic solvent thus condensed is dropped onto a liquid receiver 45 and then recovered for reuse. Likewise, the organic solvent in the form of liquid containing water which is dropped from the objects 43 is recovered by another liquid receiver 46.
Unfortunately, in the conventional drying apparatus thus constructed, it is required that an operator is highly careful with fire because the organic solvent is heated. Also, it causes energy consumption to be substantially increased due to both heating and cooling of the organic solvent. Further, it requires much time for the drying because of heating the organic solvent to form a layer of the vapor and is increased in consumption of the organic solvent due to loss by evaporation. In addition, when the objects are brought into contact with the layer of the vapor, heat of the vapor (gaseous phase) is removed by the objects to cause a rapid phase change of the organic solvent from gas to liquid. This reduces the vapor layer, to thereby cause the objects to be exposed to an ambient atmosphere, leading to problems such as contamination of the objects, a failure in drying thereof and the like. Also, there is likelihood that the organic solvent is contaminated by dust contained in the ambient atmosphere, leading to contamination of the objects.